Under unbalanced source voltage supply, considerable output second harmonics and input low-order harmonics in 3-phase PWM current-source converters (PWM-CSC) are generated. This paper proposes a new deadbeat controlle...Under unbalanced source voltage supply, considerable output second harmonics and input low-order harmonics in 3-phase PWM current-source converters (PWM-CSC) are generated. This paper proposes a new deadbeat controller based on compensation for unbalanced source voltage and current. With the proposed scheme, the second harmonics of the output current are eliminated and low-order harmonics of the source current are reduced effectively. Simulation and experimental results con- firmed the feasibility of the proposed method.展开更多
针对构网型变流器(grid-forming voltage source converter,GFM-VSC)系统在大扰动下暂态稳定问题,现有研究未能充分考虑电力电子电源暂态快速响应与控制可塑的特点。为此,以GFM-VSC为对象,借助等面积法原理与相平面图法,从能量角度揭示...针对构网型变流器(grid-forming voltage source converter,GFM-VSC)系统在大扰动下暂态稳定问题,现有研究未能充分考虑电力电子电源暂态快速响应与控制可塑的特点。为此,以GFM-VSC为对象,借助等面积法原理与相平面图法,从能量角度揭示了其暂态响应机制与传统同步机系统的差异,分析了控制塑造下GFM-VSC系统的暂态稳定机理;然后,针对大扰动下易于触发的限幅环节,分析了系统无法自主退出限幅而失稳的机制,并提出了附带电流分配系数的改进限幅策略,有效增强了系统暂态稳定性。最后,通过仿真验证了理论分析与改进方法的正确性。展开更多
In medium voltage high power applications,multi-level current source converters(CSCs)are good candidate to increase system power region,reliability,and the quality of output waveforms.Compared with widely researched v...In medium voltage high power applications,multi-level current source converters(CSCs)are good candidate to increase system power region,reliability,and the quality of output waveforms.Compared with widely researched voltage source multi-level converters(MLCs),the current source MLCs have the advantages of inherent short-circuit protection,high power capability and high quality of output current waveforms.The main features of MLCs include reduced harmonics,lower switching frequency and reduced current stress on each device which is a particularly important for high power application with low voltage and high current requirements.This paper conducts a general review of the current research about MLCs in higher power medium voltage application.The different types of parallel structure based MLCs and the modulation methodologies will be introduced and compared.Specifically,the circuit analysis of the common-mode(CM)loop for parallel structures will be conducted,the common-mode voltage(CMV)and circulating current suppression methods developed on the base of multilevel modulations will be addressed.展开更多
In this paper,to study the power loss of converter for elevator,The analysis is to establish relationship between parameters(current,voltages and losses in the inverter and converter) relevant for sizing of major comp...In this paper,to study the power loss of converter for elevator,The analysis is to establish relationship between parameters(current,voltages and losses in the inverter and converter) relevant for sizing of major components of the drive was done.) For high PWM(pulse width modulation) frequency like in elevator applications of fpwm =10kHz,switching losses are dominant and are about 2/3 of the total losses on IGBT switch.Transition from continuous 3 phase to discontinuous 2 phase PWM results in 50% reduction of switching loses on IGBT devices providing that PWM is not done over 60deg angle in a particular phase when current has maximum value.Total losses on IGBT(conduction + switching) are reduced approximately by ~1/3 what is still a significant reduction.Two phase PWM with reduced losses can be used for applications when acoustic noise due to increased current ripple is not significant and fall back solution to regular 3 phase PWM when drive operates under rare extreme conditions resulting in increased heat sink temperature.The analysis will be examined by further laboratory testing simulating 60% duty cycle on a dynamometer.展开更多
In recent years,sub-synchronous oscillation accidents caused by wind power integration have received extensive attention.The recorded constant-amplitude waveforms can be induced by either linear or nonlinear oscillati...In recent years,sub-synchronous oscillation accidents caused by wind power integration have received extensive attention.The recorded constant-amplitude waveforms can be induced by either linear or nonlinear oscillation mechanisms.Hence,the nonlinear behavior needs to be distinguished prior to choosing the analysis method.Since the 1960s,the higher-order statistics(HOS)theory has become a powerful tool for the detection of nonlinear behavior(DNB)in production quality control wherein it has mainly been applied to mechanical condition monitoring and fault diagnosis.This study focuses on the hard limiters of the voltage source converter(VSC)control systems in the wind farms and attempts to detect the nonlinear behavior caused by bi-or uni-Iateral saturation hard limiting using the HOS analysis.First,the conventional describing function is extended to obtain the detailed frequency domain information on the bi-and uni-Iateral saturation hard limiting.Furthermore,the bi-and tri-spectra are introduced as the HOS,which are extended into bi-and tri-coherence spectra to eliminate the effects of the linear parts on the harmonic characteristics of hard limiting in the VSC control system,respectively.The effectiveness of the HOS in the DNB and the classification of the hard-limiting types is proven,and its detailed derivation and estimation procedure is presented.Finally,the quadratic and cubic phase coupling in the signals is illustrated,and the performance of the proposed method is evaluated and discussed.展开更多
This paper presents a unified positive-and negative-sequence dual-dq dynamic model of wind-turbine driven doubly-fed induction generator(DFIG) under unbalanced grid voltage conditions. Strategies for enhanced control ...This paper presents a unified positive-and negative-sequence dual-dq dynamic model of wind-turbine driven doubly-fed induction generator(DFIG) under unbalanced grid voltage conditions. Strategies for enhanced control and operation of a DFIG-used back-to-back(BTB) PWM voltage source converter(VSC) are proposed. The modified control design for the grid-side converter in the stationary αβ frames diminishes the amplitude of DC-link voltage ripples of twice the grid frequency,and the two proposed control targets for the rotor-side converter are alternatively achieved,which,as a result,improve the fault-ride through(FRT) capability of the DFIG based wind power generation systems during unbalanced network supply. A complete unbalanced control scheme with both grid-and rotor-side converters included is designed. Finally,simulation was carried out on a 1.5 MW wind-turbine driven DFIG system and the validity of the developed unified model and the feasibility of the proposed control strategies are all confirmed by the simulated results.展开更多
The pulse-width-modulated(PWM)current-source converters(CSCs)fed electric machine systems can be considered as a type of high reliability energy conversion systems,since they work with the long-life DC-link inductor a...The pulse-width-modulated(PWM)current-source converters(CSCs)fed electric machine systems can be considered as a type of high reliability energy conversion systems,since they work with the long-life DC-link inductor and offer high fault-tolerant capability for short-circuit faults.Besides,they provide motor friendly waveforms and four-quadrant operation ability.Therefore,they are suitable for high-power applications of fans,pumps,compressors and wind power generation.The purpose of this paper is to comprehensively review recent developments of key technologies on modulation and control of high-power(HP)PWM-CSC fed electric machines systems,including reduction of low-order current harmonics,suppression of inductor–capacitor(LC)resonance,mitigation of common-mode voltage(CMV)and control of modular PWM-CSC fed systems.In particular,recent work on the overlapping effects during commutation,LC resonance suppression under fault-tolerant operation and collaboration of modular PMW-CSCs are described.Both theoretical analysis and some results in simulations and experiments are presented.Finally,a brief discussion regarding the future trend of the HP CSC fed electric machines systems is presented.展开更多
To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a ...To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a full bridge LLC resonant converter,three-level half bridge LLC resonant converter,and variable frequency control mode,the converter realizes an intelligent estimation of input voltage by automatically changing its internal cir-cuit topology.Under this control strategy,different input voltages determine different operation modes.This is achieved in full bridge LLC mode when the input voltage is low.If the input voltage rises to a certain level,it operates in three-level half bridge LLC mode.These switches are digital and entirely carried out by the DSP(Digi-tal Signal Processor),which means that an auxiliary circuit is unnecessary,where a simple strategy of software modification can be utilized.Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92%are developed to verify feasibility and practicability.This type of converter is suitable for applications with an ultra-wide input voltage range,such as wind turbines,photovoltaic generators,bioenergy,and other renewable energy sources.展开更多
The increase in the installed capacity of wind energy conversion systems(WECS) has triggered the devel-opment of more demanding grid codes and additional requirements on performance.In order to meet these require-ment...The increase in the installed capacity of wind energy conversion systems(WECS) has triggered the devel-opment of more demanding grid codes and additional requirements on performance.In order to meet these require-ments the industry trend has shifted to full-scale power converter interfaces in modern multi-megawatt WECS.As con-sequence,a wide variety of new power converter topologies and WECS configurations have been introduced in recent years.Among them,current source converter(CSC) based configurations have attracted attention due to a series of advantages like:simple structure,grid friendly waveforms,controllable power factor,and reliable grid short-circuit pro-tection.This paper presents the latest developments in CSC interfaces for WECS and related technologies such as modulation methods,control schemes and grid code compatibility.展开更多
This project proposes a novel dual-input matrix converter (DIMC) which is used to integrate the output of the wind energy to a power grid. The proposed matrix converter is developed based on the traditional indirect m...This project proposes a novel dual-input matrix converter (DIMC) which is used to integrate the output of the wind energy to a power grid. The proposed matrix converter is developed based on the traditional indirect matrix converter under reverse power flow operation mode, but with its six-switch voltage source converter replaced by a nine-switch configuration followed by the current source inverter (CSI). Matrix electric power conversion topologies and their switch functions are flexible and are used for specific applications. With the additional three switches, the proposed DIMC can provide six input terminals, which make it possible to integrate two independent AC sources from two independent wind turbines into a single grid tied power electronics interface. Commanded currents can be extracted from the two input sources to the grid. The proposed PI control and modulation schemes guaranteed sinusoidal input and output waveforms as well as reduced THD. The simulation results are provided to validate the effectiveness of the proposed control and modulation schemes for the proposed converter.展开更多
基金Project (No. 50477033) supported by the National Nature ScienceFoundation of China
文摘Under unbalanced source voltage supply, considerable output second harmonics and input low-order harmonics in 3-phase PWM current-source converters (PWM-CSC) are generated. This paper proposes a new deadbeat controller based on compensation for unbalanced source voltage and current. With the proposed scheme, the second harmonics of the output current are eliminated and low-order harmonics of the source current are reduced effectively. Simulation and experimental results con- firmed the feasibility of the proposed method.
文摘针对构网型变流器(grid-forming voltage source converter,GFM-VSC)系统在大扰动下暂态稳定问题,现有研究未能充分考虑电力电子电源暂态快速响应与控制可塑的特点。为此,以GFM-VSC为对象,借助等面积法原理与相平面图法,从能量角度揭示了其暂态响应机制与传统同步机系统的差异,分析了控制塑造下GFM-VSC系统的暂态稳定机理;然后,针对大扰动下易于触发的限幅环节,分析了系统无法自主退出限幅而失稳的机制,并提出了附带电流分配系数的改进限幅策略,有效增强了系统暂态稳定性。最后,通过仿真验证了理论分析与改进方法的正确性。
文摘In medium voltage high power applications,multi-level current source converters(CSCs)are good candidate to increase system power region,reliability,and the quality of output waveforms.Compared with widely researched voltage source multi-level converters(MLCs),the current source MLCs have the advantages of inherent short-circuit protection,high power capability and high quality of output current waveforms.The main features of MLCs include reduced harmonics,lower switching frequency and reduced current stress on each device which is a particularly important for high power application with low voltage and high current requirements.This paper conducts a general review of the current research about MLCs in higher power medium voltage application.The different types of parallel structure based MLCs and the modulation methodologies will be introduced and compared.Specifically,the circuit analysis of the common-mode(CM)loop for parallel structures will be conducted,the common-mode voltage(CMV)and circulating current suppression methods developed on the base of multilevel modulations will be addressed.
文摘In this paper,to study the power loss of converter for elevator,The analysis is to establish relationship between parameters(current,voltages and losses in the inverter and converter) relevant for sizing of major components of the drive was done.) For high PWM(pulse width modulation) frequency like in elevator applications of fpwm =10kHz,switching losses are dominant and are about 2/3 of the total losses on IGBT switch.Transition from continuous 3 phase to discontinuous 2 phase PWM results in 50% reduction of switching loses on IGBT devices providing that PWM is not done over 60deg angle in a particular phase when current has maximum value.Total losses on IGBT(conduction + switching) are reduced approximately by ~1/3 what is still a significant reduction.Two phase PWM with reduced losses can be used for applications when acoustic noise due to increased current ripple is not significant and fall back solution to regular 3 phase PWM when drive operates under rare extreme conditions resulting in increased heat sink temperature.The analysis will be examined by further laboratory testing simulating 60% duty cycle on a dynamometer.
基金supported by the State Grid Guide Project(No.5108-202218030A-1-1-ZN)。
文摘In recent years,sub-synchronous oscillation accidents caused by wind power integration have received extensive attention.The recorded constant-amplitude waveforms can be induced by either linear or nonlinear oscillation mechanisms.Hence,the nonlinear behavior needs to be distinguished prior to choosing the analysis method.Since the 1960s,the higher-order statistics(HOS)theory has become a powerful tool for the detection of nonlinear behavior(DNB)in production quality control wherein it has mainly been applied to mechanical condition monitoring and fault diagnosis.This study focuses on the hard limiters of the voltage source converter(VSC)control systems in the wind farms and attempts to detect the nonlinear behavior caused by bi-or uni-Iateral saturation hard limiting using the HOS analysis.First,the conventional describing function is extended to obtain the detailed frequency domain information on the bi-and uni-Iateral saturation hard limiting.Furthermore,the bi-and tri-spectra are introduced as the HOS,which are extended into bi-and tri-coherence spectra to eliminate the effects of the linear parts on the harmonic characteristics of hard limiting in the VSC control system,respectively.The effectiveness of the HOS in the DNB and the classification of the hard-limiting types is proven,and its detailed derivation and estimation procedure is presented.Finally,the quadratic and cubic phase coupling in the signals is illustrated,and the performance of the proposed method is evaluated and discussed.
基金Project (No. 50577056) supported by the National Natural ScienceFoundation of China
文摘This paper presents a unified positive-and negative-sequence dual-dq dynamic model of wind-turbine driven doubly-fed induction generator(DFIG) under unbalanced grid voltage conditions. Strategies for enhanced control and operation of a DFIG-used back-to-back(BTB) PWM voltage source converter(VSC) are proposed. The modified control design for the grid-side converter in the stationary αβ frames diminishes the amplitude of DC-link voltage ripples of twice the grid frequency,and the two proposed control targets for the rotor-side converter are alternatively achieved,which,as a result,improve the fault-ride through(FRT) capability of the DFIG based wind power generation systems during unbalanced network supply. A complete unbalanced control scheme with both grid-and rotor-side converters included is designed. Finally,simulation was carried out on a 1.5 MW wind-turbine driven DFIG system and the validity of the developed unified model and the feasibility of the proposed control strategies are all confirmed by the simulated results.
基金supported in part by the Jiangsu Natural Science Foundation of China under Grant BK20180013in part by the Shenzhen Science and Technology Innovation Committee(STIC)under Grant JCYJ20180306174439784.
文摘The pulse-width-modulated(PWM)current-source converters(CSCs)fed electric machine systems can be considered as a type of high reliability energy conversion systems,since they work with the long-life DC-link inductor and offer high fault-tolerant capability for short-circuit faults.Besides,they provide motor friendly waveforms and four-quadrant operation ability.Therefore,they are suitable for high-power applications of fans,pumps,compressors and wind power generation.The purpose of this paper is to comprehensively review recent developments of key technologies on modulation and control of high-power(HP)PWM-CSC fed electric machines systems,including reduction of low-order current harmonics,suppression of inductor–capacitor(LC)resonance,mitigation of common-mode voltage(CMV)and control of modular PWM-CSC fed systems.In particular,recent work on the overlapping effects during commutation,LC resonance suppression under fault-tolerant operation and collaboration of modular PMW-CSCs are described.Both theoretical analysis and some results in simulations and experiments are presented.Finally,a brief discussion regarding the future trend of the HP CSC fed electric machines systems is presented.
文摘To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a full bridge LLC resonant converter,three-level half bridge LLC resonant converter,and variable frequency control mode,the converter realizes an intelligent estimation of input voltage by automatically changing its internal cir-cuit topology.Under this control strategy,different input voltages determine different operation modes.This is achieved in full bridge LLC mode when the input voltage is low.If the input voltage rises to a certain level,it operates in three-level half bridge LLC mode.These switches are digital and entirely carried out by the DSP(Digi-tal Signal Processor),which means that an auxiliary circuit is unnecessary,where a simple strategy of software modification can be utilized.Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92%are developed to verify feasibility and practicability.This type of converter is suitable for applications with an ultra-wide input voltage range,such as wind turbines,photovoltaic generators,bioenergy,and other renewable energy sources.
文摘The increase in the installed capacity of wind energy conversion systems(WECS) has triggered the devel-opment of more demanding grid codes and additional requirements on performance.In order to meet these require-ments the industry trend has shifted to full-scale power converter interfaces in modern multi-megawatt WECS.As con-sequence,a wide variety of new power converter topologies and WECS configurations have been introduced in recent years.Among them,current source converter(CSC) based configurations have attracted attention due to a series of advantages like:simple structure,grid friendly waveforms,controllable power factor,and reliable grid short-circuit pro-tection.This paper presents the latest developments in CSC interfaces for WECS and related technologies such as modulation methods,control schemes and grid code compatibility.
文摘This project proposes a novel dual-input matrix converter (DIMC) which is used to integrate the output of the wind energy to a power grid. The proposed matrix converter is developed based on the traditional indirect matrix converter under reverse power flow operation mode, but with its six-switch voltage source converter replaced by a nine-switch configuration followed by the current source inverter (CSI). Matrix electric power conversion topologies and their switch functions are flexible and are used for specific applications. With the additional three switches, the proposed DIMC can provide six input terminals, which make it possible to integrate two independent AC sources from two independent wind turbines into a single grid tied power electronics interface. Commanded currents can be extracted from the two input sources to the grid. The proposed PI control and modulation schemes guaranteed sinusoidal input and output waveforms as well as reduced THD. The simulation results are provided to validate the effectiveness of the proposed control and modulation schemes for the proposed converter.